Smokeless powder



Patented Sept. 12, 1944 SMOKELESS POWDER Elton R. Allison, Washington, Hercules Powder Company,

D. 0., assignor to Wilmington, Del.,

a. corporation of Delaware No Drawing. Application April 1, 1942, Serial No. 437,229

ber of high breech pressure shots is materially re- 6 Claims.

This invention relates to an improved smokeless powder and to a method for its preparation.

'In more particular, the invention relates to an improved smokeless powder, especially adapted for firing at sub-zero temperatures and to a method of compounding such a powder.

In order to obtain progressive-burning smokeless powder, the art has developed various methods for surface-coating powder grains .with a variety of materials. This surface coating so modifies the various powder grains that their burning characteristics may be controlled, i. e., as the powder burns from the surface inwardly, the successively exposed surfaces contain gradually less and less of the surface-coating materm], and the combustion of the grains increases in speed as time of burning progresses.

Coatings of many different types have been used and each one has advantages which make powder so coated suitable for special purposes. Some disadvantages have been encountered with surface-coated powders due to fouling of the barrel, difllculties of ignition, high breechpressures when fired at low temperatures, clustering of the grains after coating, and the like, but for the most part, coated powder grains have been found very desirable.

It has been shown in the prior art that one of the most diflicult problems facing the manufacturer of progressive-burning powder is the compounding of progressive-burning powder grains which will perform satisfactorily in rifles when they are shot at normal temperature, and also when they are shot at sub-zero temperature. The use of rifles at sub-zero temperature is becoming increasingly important because of aerial warfare. The temperatures experienced in aerial combat are usually well below zero, sometimes dropping as low as or 50-F., and the performance of rifles, especially the rifles of the machine-gun type, is of extreme importance as a hangflre or an exceptionally high breech pressure may disrupt the workings of the gun to a point where the aircraft is forced out of battle.

The problem of controlling the operation of powders at sub-zero temperatures is shown by prior art Patent 2,159,208. Thus, improvements over normal powder may be obtained by colloiding the nitrocellulose with anhydrous solvent alcohols instead of the normally water-containing solvents. The alcohol, in general use, contains usually about 5% water and produces a powder grain which has a decided tendency to cause high breech pressures, especially when the powder is of the double base type, i. e., containing in addition to nitrocellulose, a liquid explosive nitric ester such as nitroglycerin. The colloiding of the powder with. anhydrous solvents produces a grain structure which, upon firing at low temsure. gives improved results because the numduced.

In addition to the use of anhydrous solvents, the control of high breech pressure shots obtained when firing a rifle at sub-zero temperature may be alleviated by the use of a particular coating method. Thus, for example, U. S. Patent 2,179,- 330, shows that a double base powder, when coated at a temperature below 55 C. with various deterrents, produces a flnished powder that is characterized by a minimum number of high breech pressure shots.

Although the prior art has shown methods of reducing the number of high breech pressure shots obtained with various double base progressive-burning powders when they are flred at subzero temperature, the difliculties encountered due to hangiires, i. e., the delay of actual ignition of the powder and increased time that the bullet is in the barrel after the primer has been struck has not been adequately solved. The hangflre presents a very serious disadvantage, especially to the operation of rapid fire rifles, such as the automatic rifle and the machine gun, and it is absolutely necessary that a powder be produced which prevents hangflres when the powder is fired either at normal temperatures or at sub-zero temperatures. In addition to a powder which will not cause hangfires, the powder should also be characterized by a burning characteristic which will not tend to give excessively high breech pressures.

It is an object of this invention to produce a progressive-burning smokeless powder that is suitable for firing at sub-zero temperatures and which will not develop hangflres.

It is another object of this invention to produce a smokeless powder composition which is easily ignited, which burns at proper pressures to give desired ballistics and which may be used at normal or sub-normal temperatures without danger of hangflres or high breech pressures,

The objects of this invention have been accomplished by producing a smokeless powder composition which comprises an admixture of coated double base powder grains which, in themselves, will not produce excessively high breech pressures when fired at sub-zero temperatures and single base powder grains of approximately the same granulation as the said double base powder grains.

In more particular, the new and improved powder, in accordance with the present invention, is manufactured by mechanically admixing powder grains of the double base and single base types together. The double base component provides the necessary power, furnishes the ballistics desired in regard to velocity, and maintains the breech pressure within ranges which will not be harmful to the rifle barrel, while the single base powder component provides the necessary ease of ignition and insures against hangfires. The admixture need only contain a minor amount of single base powder, but this single base powder,

must be of a granulation which will not segregate after being evenly distributed throughout the double base powder grains. In order to accomplish this desirable intimate admixing, it has been found that grains of substantially the same granulation and substantially the same specific gravity give the best results.

The admixtures which have been found very useful for controlling breech pressures and hangfires are admixtures of coated double base smokeless powders and single base smokeless powders in which the single base component is present within the range of between about. and about 30%. Reduction of the single base component below about 10% tends to cause hangfires, while increasing the percentage above about 30% prevents the ballistic advantages inherent within double base powders from exerting their true influence.

The double base powder grains which have been found most useful for admixture with single base grains in accordance with this invention are any powder grains which have been manufactured in a manner that provides ballistics which will not increase breech pressures when fired at sub-zero temperatures such as, for example, as disclosed by U. that the preferable means of producing such a powder is to provide a base grained double base smokeless powder and surface modify this base grain with an admixture of a non-volatile, nonexplosive organic material which is a non-solvent for the nitrocellulose but which is compatible therewith, and a solvent for the said nitrocellulose. Thecoating procedure is carried out at a temperature less than about 55 C. as temperatures higher than about 55 C. will produce a coated powder which, if shot after sub-zero temperatures, will produce high breech pressures.

Examples of the deterrent which may be utilized to coat the grains of the double base smokeless powder at below 55 C. and in conjunction with a solvent for the nitrocellulose may be, for example, the alkyl esters of the fatty acids, terpene phthalates, rosin esters, synthetic lacquer 8. 2,159,208 and 2,179,330. It was found a normal solvent recovery, water-dry, air-dry, glazing and sieving operations are carried out.

Now having described the manufacture of the double base powder grains and the single base powder grains which may be used as components of powder produced in accordance with this invention, there follows a description of tests of various powders and admixtures which illustrate by comparison the invention and conclusively show the nature of the improvements obtained.

COIPARISON I In this comparison the improvement obtained by using a blend of powders in accordance with this invention regarding hangfires is shown.

Emmple A A double base powder containing 20% nitroglycerin and granulated .045-.015 x 1/11 was coated with 1.25% rosin and 1.5% DNT and then -50 F. The results of pressure and barrel time from firing 10 rounds in a .25/ W. C. F. rifle with a 23 grain charge were:

Pressure Barrel time, sec/Lilli Temp.

Min. Mean Max. Min. Mean Max.

77F 211,100 33,000 30,400 2.44 zoo ans 50"F 21K!) 28,4) 31.000 2.80 4.27 13.3

These results show a definite hangfire tendency at low temperatures.

Example 8 40 Four parts by weight of a double base powder resins as the modified or unmodified polyhydric alcohol-polybasic acid resins, ated rosins, and the like.

The solvents which may be used for assisting in the coating of the double base smokeless powder grains with the above-described deterrents are, for example, ethyl acetate, butyl acetate, mixtures of alcohol and ether andany other solvents for nitrocellulose which have a boiling point of from about 35 C. to about 180 C., and preferably from about 70 C. to about 130 0., or such non-volatile solvents as the alkyl phthalates. The process of producing such surface-modified double base powder grains is more fully described rosins, hydrogenin U. 8. Patent 2,179,330.

P wder grains which may be I used for the present invention are prepared in The single base the normal accepted manner, 1. e., the nitrocellulose is colloided with solvents such as etheralcohoL'extmded through dies and granulated to the desired grain size. Thereafter, the solvent is recovered and the glazed, and sieved.

A desirable single base powder grain for use in accordance with this invention may be produced by.collolding 100 pounds of nitrocellulose content of about 13% and conpowder water dried, air dried,

having a nitrogen similar to Example A was blended with one part by weight of a single base powder having substantially the same granulation and specific gravity and was fired at -43.6 1". with a 23.3 grain charge.

Pressure Barrel time, see/1,000

Temp.

Min. Meau Max. Min. Mean Max.

These results show that the additlonof base smokeless grains'prevents excessive time.

single barrel Example B1 A duplicate of Example B was carried out with a similar but difierent lot of double base smoke- A double base powder containing 20% nitroglycerin and coated with 1.5% rosin and 1.5%

Ketonone E was tested at a low temperature.

This powder did not give excessive pressures at the low temperatures but gave hangfires in the similar results.

.25/35 w. c. F. rifle using a 20.0 min charge.

The results are as follows:

Preuure Barrel time, sea/1,000

Temp.

Min. Mean Max. Min. Mam Max. -02.0r 2a000\s1,s00 30,000 221 004 0.01

Example D To the powder of Example C was added 25% of a single base powder and the admixture tested in the .25/35 W. C. F. rifle using a 22.0 grain charge.

The results were as follows: 7

Pressure Barrel time, sea/1,000

Temp.

Min. Mean Max. Min. Mean. Mar.

Cosmmrson II In Comparison I powders were tested in the .25/35 W. C. F. rifle. In this comparison similar tests were made in the 30.06 Springfield to show the reduction of hangfires by usingthe powder admixtures of this invention.

Example E A double base powder containing 20% nitroglycerin and granulated .045 x .015 x1091 was coated with 1% rosin, 1% butylacetyl ricinoleate and 2% Ketonone E when fired at low temperatures did not develop excessive pressures but hangfires were encountered. The results obtained with a 53.0 grain charge were:

Pressure Barrel time, see/1,000

Temp.

Min. Mean Max. Min. Mean Max.

Example F To the powder of Example E was added single base powder. When the admixture was fired using a 49.6 grain charge, the results were:

Pressure Barrel time, sea/1,000

Temp. I

Min. Mean Max. Min. Mean Mar.

A blend using 25% single base powder gave Comrmson' III In this comparison is shown the excessive pressures obtained when double base powders are shot at low temperatures and the normal pressures obtained when single base powders are admixed therewith.

Example G A double base powder containing nitroglycerin, granulated .045 x .015 x .091 and coated with 1.25% rosin and 1.25% dinitrotoluene was fired in a .25/35 W. C. F. ride at 78 F. and -49" F. using a 23 grain charge. The results were:

v Pressure Temp.

Min. Mean Mar.

. Example H To the powder 01' Example G was added 20% single base powder having approximately the same granulation and the admixture was fired in the .25/35' W. C. F. rifle at 82 F. and -49 F. using a 22.8 grain charge. The results were:

Pressure Temp.

Min. Mean Max.

Example I A double base powder containing 20% nitroglycerin, granulated .045 x .015 x .091 and coated with 1.5% rosin and 1% dlnitrotoluene was fired in the .25/35 W. C. F. ride at 76 C. and '-4'l,.2 I". using a 23.5 grain charge. The results were:

Temp.

Min Mean Max Example .1

To the powder of Example I was added 20% single base powder having approximately the same granulation and the admixture was fired in the .25/35 W. C. F. rifle at 78 F. and 45.4 F. usin a 23.7 grain charge. The results were:

PteJ e Temp.

Min. Mean Max.

The above blends gave satisfactory ballistics at low temperatures while the double base powder grains alone when fired at low temperatures showed excessive pressures.

In the above examples, the results are an average of ten rounds, except in Examples B, F and H. In these examples. five rounds were fired. Further, in the above examples in which the .25/35 W. C. I. rifle was used, all bullets were Winchester 117 grain S. P. bullets except those in Examples C and D which used Remington 117 grain Express mushroom bullets. The bullets used in the .30-06 Springfield rifle were F. A. 178 grain 9 B. T. bullets. Also, in the above examples. all pressure results are expressed in pounds per square inch.

In the above examples. most results have been obtained in the .25/35 W. C. 1". rifle but these improvements are also obtained in the various known rifles such as the .30-06 Springfield, .303 British, .30 W. C. I". and other such rifles.

From the above examples, the advantages 0! using powder in accordance with this invention admixture of double base coated grains and sinare shown to be the prevention or excessively gle base uncoated grains, said grains having up high breech pressures at sub-zero temperatures proximately the same granulation and specific and the elimination of ha'nsfires during operagravity, the double base grains coated with an tion or rifles at sub-zero temperatures. These 5 admixture of non-volatile, non-explosive organic two items are most advantageous when the riiie deterrent material which is a non-solvent for the is used in aerial wariar as in most aerial war-- trocellulose but compatible therewith, and a fare the temperature is quite low. However, non-volatile solvent for said nitrocellulose, many other occasions arise where riiies are opwhereby a propellent powder is produced which erated in sub-zero temperatures and this inven- .10 expels a bullet from a barrel in approximately tion therefore finds many applications. the same length oi time at sub-zero tempera- What I claim and desire to protect by Letters tures as at normal temperatures said single base Patent is: grains being present in amount from about to 1. A propellent powder charge including an abo t 30% by weight, admixture 0! double .base smokeless powder sur- 5 5. A propellent powder adapted for use at subiace modified and characterized by producing zero temperatures which comprises a blend oi breech pressures when fired at sub-zero tempera- I grains of double base progressive-burning smoketures which are not substantially greater than less powder, characterized by an ability to mainthose produced when fired at ordinary temperatain normal breech pressures when fired at subtures, and a single base propellent powder in an zero temperatures and a single .base progressiveamount from about 10 to about 30% by weight, burning smokeless powder characterized by a sufiicient to. allow ready ignition, whereby ignigranulation density substantially equivalentto the tion and firing characteristics are obtained granulation and densityof the said double base. which prevent hangfires at sub-zero temperapowder, said blend. including suflicient single tux-es, base powder grains to eflect easy ignition and 2. A propellent powder charge comprising said blend characterized by an ability to expel a coated double base grains and uncoated single bullet-from a barrel at sub-zero temperatures in base grains of substantially the same granulation substantially the same length, of. time required and specific gravity, said powder charge characto expel said bullet at normal temperatures said terized by an ability of expelling a bullet from, single base grains being present in amount from a rifle in substantially the same length of time about 10 to about 30% by weight. at sub-zero temperatures as is required for ex- 6. An improved propellent powder comprising pelling said :bullet at normal temperatures said an intimate admixture ,01' double baseand single single base grains being present in amount from base smokeless powder grains. said double base about 10 to about 30% by weight. 5 powder being surface modified with an admixture 3. A propellent powder charge comprising an of a non-volatile, non-explosive organic deterrent admixture of coated double base powder grains material which is a non-solvent for the nitroceland single base grains, said grains being of subiulose but compatible therewith, and a non-volastantially the same granulation and specific gravtile solvent of said nitrocellulose, said single base ity, and the said double base grains coated with. 40 powder present in an amount from about 10 to an admixture or an alkyl ester of a higher Iatty' about 30% by weight, suflicient to characterize acid and a non-volatile solvent for the said 'nithe admixture as being of normal ignition and trocellulose said single base grains being present burning properties whenfired at sub-zero temin amount from about 10 to about 30% by weight. peratures.

'4. A propellent powder adapted for use at sub-, 5 ELTON R. ALLISON. zero temperatures, which powder comprises an 

